PROJECT SUMMARY Project 2: FSHD Drug Discovery There are currently no treatments for FSHD, and therapy development is a critical unmet need in the field. Indeed, until recently therapeutic development for FSHD has been virtually non-existent. The major reasons for this are that the pathogenic mechanisms underlying FSHD have only recently started becoming clear and there have been no accepted animal models of the disease. Importantly, we now have a viable target for therapy and new cell and animal models of FSHD, including ones developed by the Wagner, Kunkel and Harper labs. The emergence of an understanding of DUX4 pathophysiology and novel animal models of the disease now provide opportunities to develop novel FSHD-targeted therapies for the first time. We believe that one approach to FSHD therapies should center on inhibiting DUX4 action, and this is the focus of Project 2. DUX4 is a transcription factor and may activate genes and pathways that are incompatible with healthy muscle. The goal of Project 2 is develop novel approaches to FSHD drug discovery focused on inhibiting the toxic effects of DUX4 protein, and we propose to accomplish this on two levels. In Specific Aim 1 we will use an unbiased approach to identify and inhibit DUX4-activated genes and pathways that contribute to its toxicity; and in Specific Aim 2, we will identify and characterize compounds that can interfere with DUX4 protein post- translational modifications required for its toxic effects. Thus, our approach will attack DUX4 toxicity by inhibiting the protein through two different mechanisms. Using a combination of cell- and animal-based testing, the overall goal of this Project is to identify compounds that demonstrate efficacy for long-term dosing in FSHD patients, with an eye towards IND review.